UV induced permanent gratings in Ce 3+ or Eu 2+ doped PZG glass thin-film waveguides deposited on CaF 2 substrates

Abstract

Ce 3+ or Eu 2+ doped PZG (PbF 2, ZnF 2, GaF 3) glass thin films fabricated by vapor phase deposition on CaF 2 substrates have been shown to possess high photosensitivity. As an illustration, strong permanent gratings have been written in the PZG glass by using a continuous wave UV laser ( λ = 244 nm). The kinetics of the grating growths were monitored by probing the efficiencies of the holograms at a wavelength of 633 nm. The mechanisms that could form the gratings have been analyzed. The UV induced changes in absorption coefficient at 633 nm or the UV induced surface modulation turned out to be too low to explain the order of magnitude of the grating efficiency. The gratings are assumed to come from changes in refractive index as high as 1.3 × 10 −2 and 3.9 × 10 −3 in the Eu 2+ and Ce 3+ doped samples respectively.